1. Field of the Invention
The present invention relates to a tyrosinase inhibitor extract from lemon peels.
2. Description of the Prior Art
Melanin plays an important role in protecting human body from the harmful effects of ultraviolet rays. Melanin is also an important factor in medical science and cosmetology. It is known that melanin is formed or synthesized in skin tissues. Excessive amounts of melanin darken the skin, and the nonuniform distribution of melanin causes chloasma and ephelis, both of which are skin disorders. The biosynthesis pathway of melanin involves the catalytic hydroxylation of tyrosine to L-3,4-dihydroxyphenylalanine (L-DOPA) and the conversion of L-DOPA to dopachrome. The more effective way to inhibit the synthesis of melanin is to block the hydroxylation of tyrosine.
Conventionally, tyrosinase inhibitors have been used to decrease the level of melanin in the skin and thereby produce a lightly pigmented skin. A variety of whitening cosmetics have been proposed or investigated and developed in order to remove spots, such as stains, and freckles, appearing on the skin and to provide a whitening effect on the skin. For example, peroxides, ascorbic acid, kojic acid, hydroquinone, glutathione, arbutin and cysteine have been developed to whiten skin. However, the conventional whitening agents have various disadvantages. For example, peroxides are unstable and have little effects on reducing the pigmentation in practical applications. Ascorbic acid is not an effective whitening agent because of its low activity in inhibiting tyrosinase and low stability. U.S. Pat. No. 6,365,137 indicates that kojic acid can be used as an inhibitor of tyrosinase. Kojic acid inhibits the activity of the enzyme by chelating the active site of tyrosinase with a copper ion. However, is it not appropriate to use kojic acid in cosmetics because it is unstable in the process of cosmetics. U.S. Pat. No. 5,523,077 mentions that hydroquinone can be used as a whitening agent. Hydroquinone is a competitive inhibitor, which causes adverse effects in skin such as irritation.
There has been a high demand of medicines or cosmetic which have advantageous skin whitening effects without adverse effects.